Season 1

While running late for class, Kenichi bumps in to the new transfer student Miu. At the karate club, Kenichi is challenged by another student Daimonji for a match. With the loser losing the right to be a member of the club. On the way home, Kenichi is awed when he sees Miu easily defeat a group of thugs. On Miu's advice, he heads to the Ryōzanpaku dojo to train in martial arts.

Kenichi begins his training at the Ryōzanpaku dojo under the guidance of Akisame. The training focuses on building strength and stamina. Concerned about Kenichi's fight with Daimonji, Miu secretly teaches him a stepping technique to maneuver around. Even though Kenichi is able to defeat Daimonji at the challenge, he yields his membership of the karate club after being accused of using a throw in a karate match.

After watching Kenichi defeat Daimonji, Tsukuba, the strongest member of the karate club, gets suspicious of Kenichi's abilities. At the school Miu, joins the girl's gymnastics club and soon becomes the center of attention after displaying her abilities at gymnastics. Kenichi desperately tries to avoid Tsukuba, but is soon caught and gets beaten to a pulp. Seeing Kenichi repent his loss to Tsukuba, Akisame decides to start training him in some martial arts techniques.

Kenichi is easily defeated by Tsukuba despite his heavy training, so he becomes greatly demotivated. With a desire to become stronger and more courageous, Akisame-sensei agrees to finally teach him martial art fighting techniques. Kenichi is put through more rigorous training from the four masters of martial arts. Sakaki-sensei takes a liking to him, so he teaches him a technique that a Sports Karate Style user is vulnerable to. Eventually Kenichi runs into Tsukuba and fights him again, this time he uses the techniques taught to him and he emerges victorious in the battle. Little does he know what troubles he will face as a result of it in the future.

With the news of Kenichi's victory over Tsukuba spreading all over, the strongest gang in the prefecture Ragnarok now has their eyes set on Kenichi. All Kenichi can do now is to train and prepare for the worst. For a change of pace, his teachers suggest that he goes on a date with Miu but they seem to have an ulterior motive.

Kenichi decides to spend the entire weekend at the Ryouzanpaku dojo and train for his imminent fights. His little sister then goes to check out this dojo, to see what kind of torturous things he's going through.

Kenichi is with fellow gardening club member Izumi, enjoying what is left of his peaceful life because following this he has more extensive training to do. During his training with Miu it doesn't take long before he runs into the Ragnorak and it is Taichi Koga the kicker he is up against.

The attacks on Kenichi are now becoming a daily occurrence and one day his opponent ends up pulling out a knife against him. Because it was his first time against a weapon, Kenichi freezes up, forcing Miu to save him. Now Shigure-sensei, the weapon specialist, has now decided to teach Kenichi the basic art weaponry.

With Kenichi's training with Apacahi always ending the same, Apachai is trying to learn of a way to go easy on him. Will Apachai ever learn how to go easy on Kenichi, during training?

Takeda Ikki, the puncher from the Ragnorak gang, is still searching for Kenichi but has had no luck so far. So he decides to hold some of Kenichi's so called friends hostage to lure him out. Now it is the time to see if Kenichi's training on Muay Thai, with Apachai, had an effect.

It's the continuation of Kenichi's intense fight with Takeda and Kenichi seems to have the upper hand but his kindness may prove to be his downfall. Kenichi is also wondering what made such a promising boxer like Takeda to become a delinquent.

Kenichi feels uneasy about how he should express his feelings to Miu. After Kisara hears of Takeda's defeat Tsuji Shinnosuke is sent to kill Kenichi, however he invites him to join his gang instead. When Kenichi refuses and debunks his way of thinking, Shinnosuke challenges him to a fight.

All of Kenichi's attacks seem to have no affect on Shinnosuke. Even though Kenichi is stronger, his opponent has more fighting experience so he is still at a disadvantage. Miu is not allowed to come to his aid because it would hurt Kenichi's pride. Kenichi becomes careless and is knocked to the ground and is about to be torn apart, Takeda comes and punches Shinnosuke to one side and escapes carrying Kenichi back to the Ryouzanpaku dojo. To Kenichi's dismay his masters all criticise him for being defeated, because it means it will lead to further defeats. Niijima continues to spread his manipulated version of the news throughout the whole school. After his defeat has been revealed to everyone, he is constantly chased around by school delinquents. All of the masters at the dojo decide that Kenichi should be taken in as a true disciple of Ryozanpaku, meaning he should stay there and must live only for martial arts.

After his defeat with Shinosuke Tsuji, the masters decided to have Kenichi live with them. This would include 24 hour hell-like training. Kenichi accepts with the idea that he would be living with Miu under the same roof. Kensei later drags Kenichi do a "special training" with him by tryring to peek on Miu and Shigure's bath unnoticed.

Honoka decides to infitrate the Ryōzanpaku by herself, much to her despair.

Kenichi and Miu's homeroom teacher pays a visit on Ryōzanpaku to check on her living conditions, and the members of the dojo decide to forge a story to deceive them.

Rivals from another dojo break into Ryōzanpaku to challenge their masters, but only with Kenichi and Miu present at the moment, they end up having to confront them by themselves.

The gang leaves with Honoka to a special summer spot.

Kisara officially becomes one of the eight fists of Ragnarok, the highest ranked members of the organization.

After becoming one of the eight fists, Kisara starts to hunt on those who deserted her. Takeda is attacked by Kisara's gang.

Kenichi and Miu aid Takeda and Ukita against Kirara's army.

Niijima puts his master plan to create his personal legion in motion.

Hoping to win Kenichi's affection, Izumi seeks for Nijima's aid and ends up paying a visit to Ryouzanpaku.

Natsu Tanimoto, the president of the drama club, invites Miu to perform "Romeo and Juliet" together at the school's play, to the despair of Kenichi.

Eager to have a rematch with Miu, Kisara and her crew set for the school, but Kenichi discover her intentions and decides to stand in her way to protect the play.

Kenichi discovers that Tanimoto is in fact Hermit, the 6th fist of Ragnarok, and must fight for his life against him.

Kensei Ma sneaks out or Ryouzanpaku to solve a family problem of his, but is followed by Kenichi, who ends up meeting his daughter Renka.

Kenichi receives an anonymous love letter, and while going to meet the person who wrote it, he ends up seeing Niijima and his Shinpaku comrades in trouble.

Ragnarok's Loki and Siegfried capture Niijima and Kenichi goes for his rescue along Miu.

Kenichi finds himself in dificulties against Seigfried, until he starts to put into practice all of the fruits of his training.

Hermit reappears eager for another fight against Kenichi, but he ends up having a sudden encounter with Honoka, unaware of who she is.

Loki kidnaps Honoka and attracts Kenichi to an old church, where he meets Hermit, and their fight begins.

During his fight with Kenichi, Hermit's tragic past is revealed.

Kenichi and Hermit's fight is interrupted by Loki, who using Honoka as a hostage, renders Kenichi unable to fight back, much to Hermit's anger.

Even after rescuing Honoka and breaking his ties with Ragnarok, Tanimoto is determined to finish his fight with Kenichi.

Renka discovers where Kensei Ma is living and appears in Ryouzanpaku, determined not only to bring her father back home, but to win Kenichi's heart too, much to Miu's jealousy.

Instead of waiting for another attack from Ragnarok, Kenichi decides to take the initiative and confront Thor, another member of the Eight Fists, after he hears about his location from Niijima.

Thor gets punished by the rest of the Eight Fists League after he chooses to leave the gang. Kisara's unwillingness to join in the punishment makes the others suspicious of her allegiance. Later, Kenichi and Miu spots Kisara taking care of an abandoned kitten, and decides to help her find a home for the kitten. Seeing that Kisara has made contact with Kenichi and Miu, Freya's personal guards attack her for her supposed betrayal.

While Miu takes the kitten to a vet, Kenichi tries to protect Kisara from the Valkyries unit, but his oath to not hit women puts him at a serious disadvantage against them, until Shigure comes to his aid.

While trying to recall his memories involving his ying-yang badge, Kenichi ends up meeting Odin, the supreme leader of Ragnarok, and their past connection is revealed

Kenichi fails to convince his childhood friend to reconsider and must face his amazing power. Meanwhile, Niijima tries to recruit Tanimoto to the Shinpaku Alliance using a trump card of his.

Kenichi trains with the Elder himself in order to surpass Ryuto's technique by training in the center of Japan called Yamagata which Kenichi has to survive in for 7 days and 7 nights but, can he survive? And Niijima tries to recruit Kisara by using her love for cats.

While training in the mountains, Kenichi gets lost but is rescued by a mysterious man named Ogata Ishinsai, and receives from him a tempting proposal that could change his destiny.

Kenichi continues his training with The Elder while the Shinpaku Alliance tries to develop a unification with Kisara's subordinates. Meanwhile, Berserker and Freya begin to hunt down the Shinpaku Alliance.

Siegfried appears in the last moment to protect Niijima from Berserker. Meanwhile, Miu deals with the Valkyrie unit by herself as Kisara has an one on one match with Freya.

Ragnarok discovers Niijima's Shinpaku Alliance hideout. Loki has his underlings surrounding the building to put an end to the Shinpaku Alliance. The rival gangs go all out in this decisive battle. Kenichi receives a message from Niijima and becomes concerned about the situation back home.

Kenichi arrives just in time to save his comrades. Kenichi is enraged after discovering the defeat of Takeda, Ukita and Siegfried so he charges towards Berserker but Hermit stops him. Hermit fights Berserker instead so that Kenichi is at his best physical form when he fights Odin. Berserker becomes excited in the fight with Hermit and unleashes his most feared fighting style, Berserk mode.

Berserker has been defeated by Hermit, so Kenichi challenges Odin to a second fight. Ryoto accepts the challenge and the long awaited battle begins. Kenichi makes full use of the training he had received from Furinji-sama. Kensei eagerly watches the fight between First Fist Odin and Kenichi from a distance.

Unable to evade Ryuto's punches at all, Kenichi starts to counter attack by constantly changing his fighting style, imitating his masters' personalities (to their combined horror and amusement).

Cornered by Kenichi's unexpected reaction, Ryuto utilizes a dangerous technique to rise up his power beyond his body's limits, and the reason for his grudge on him is revealed. As their fight comes close to a conclusion, Kenichi continues determined to win, not only for his own sake, but for his childhood friend's too.